The metabolism of chondroitin SO4 in cultured chondrocytes from histologically distinct regions of the chick embryo tibiotarsus will be studied. Work with focus on the biosynthesis, secretion and catabolism of chondroitin SO4 and on the changes in these activities during the terminal stages of chondrocyte differentiation in tibiotarsus development. The rates of collagen synthesis, secretion, and maturation in these cells will also be determined.